Insert sintered part and manufacturing method for same

ABSTRACT

By using a forming die having a fixed die and a movable die moving along a parting surface on the fixed die and by moving the movable die along the parting surface, to press and hold a sintered part between the movable die and the fixed die, to form a cavity around the sintered part except parts which abut on the fixed die and the movable die by the forming die, and to fill the cavity with melted material which becomes an exterior part, so that the sintered part and the exterior part are integrated by insert molding.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Patent Application No. PCT/JP2021/002402 filed onJan. 25, 2021 and claims the benefit of priority to Japanese PatentApplication No. 2020-014473, filed on Jan. 31, 2020, the contents of allof which are incorporated herein by reference in their entireties. TheInternational Application was published in Japanese on Aug. 5, 2021 asInternational Publication No. WO/2021/153488 under PCT Article 21(2).

FIELD OF THE INVENTION

The present invention relates to an insert sintered part in which asintered part such as a sintered bearing and an exterior part areintegrated and a manufacturing method thereof.

BACKGROUND OF THE INVENTION

A sintered bearing can be used for a long time without oiling, so thatit is broadly used as a bearing of a rotating shaft of an automobile, ahousehold electric appliance, acoustic equipment and the like, sincelubricant which has been beforehand impregnated inside a sintered bodyexudes out by pumping action by rotation of a shaft and thermalexpansion by friction heat lubricates a friction surface.

This sort of sintered bearing is integrated with an exterior part suchas a housing by insert-molding and incorporated with a structure such asan automobile. In this case, since a radial load and a thrust load areapplied on the sintered bearing, it is necessary to prevent a rotationabout the exterior part and dropping off in an axial direction.

For example, Japanese Unexamined Patent Application, First PublicationNo. 2003-159720 discloses a sintered bearing (a sintered part) in whichbottomed grooves extending from both end surfaces along the axialdirection along the axial direction are formed at positions that do notcoincide with each other in the axial direction. It is described thatthe rotation stopper and prevention of dropping off in the axialdirection by forming a resin part (exterior part) by insert-molding onthe outer peripheral part of the sintered bearing integrally, so thatthe resin is entered into the bottomed grooves.

Japanese Unexamined Patent Application, First Publication No.2003-193113 discloses a sintered bearing (sintered part) in which groovepart extending along an axial direction and an enlarged-diameter partextending in a circumferential direction are formed on an outerperipheral surface thereof and the groove part divides the extension ofthe enlarged-diameter part in the circumferential direction. By forminga resin part integrally on the outer peripheral part of this sinteredbearing by insert-molding, the sintered bearing is prevented fromrotating to the resin part since the resin enters the groove part, andthe sintered bearing is prevented from dropping off since theenlarged-diameter part is integrated to cut into the resin part.

CITATION LIST Patent Literature [Patent Literature 1] JapaneseUnexamined Patent Application, First Publication No. 2003-159720 [PatentLiterature 2] Japanese Unexamined Patent Application, First PublicationNo. 2003-193113 Technical Problem

When a sintered part such as this type of sintered bearing or the likeis insert-molded, by forming a space (cavity) on the outer peripheralpart of the sintered part disposed in a forming die and injecting meltedresin (melted material) into the cavity to be filled, the outerperipheral part of the sintered part is covered with the resin part. Thecavity is formed around the sintered part where both end surfaces areabutted to the forming die.

However, it is difficult to manufacture the sintered parts having thesame dimension without dispersing of height. For example, in a case inwhich the height of the sintered part is lower than a designeddimension, a gap is made between the end surface of the sintered partand the forming die, so that melted material enters the gap and a filmis made on the end surface of the sintered part. Whereas, in a case inwhich the height of the sintered part is higher than the designeddimension, a gap is made at a parting line since the forming die ispressed by the sintered part, so that the melted material is forced outfrom the gap to form burrs.

The present invention is achieved in consideration of the abovecircumstances and has an object to appropriately integrate the sinteredpart and the exterior part such as a resin part by insert-molding evenwhen the height of the sintered part such as sintered bearingsirregular.

SUMMARY OF THE INVENTION Solution to Problem

A method of manufacturing an insert sintered part of the presentinvention includes a forming step of a sintered part forming a sinteredpart having a first end part and a second end part by powder molding;and an insert-molding step of forming an insert sintered part in whichan exterior part is integrated to an outer peripheral part of thesintered part, wherein a forming die used in the step of insert-forminghas a fixed die and a movable die; a parting surface in which the fixeddie and the movable die abut is formed along a movement direction of themovable die. In this manufacturing method, the step of insert-forminghas: a die-clamping step in which the sintered part is held between thefixed die and the movable die, the movable die is moved along theparting surface, and the sintered part is pressed against the fixed dieby the movable die, to form a cavity around the sintered part bycovering a region of the sintered part with a gap excepting a part wherethe first end part abutting the fixed part, and a part where the secondpart abutting the movable die; and a filling step after the die-clampingstep filling the cavity with a melted material being formed into theexterior part.

An insert sintered part includes a sintered part having a first end partand a second end part and an exterior part which is formed integrallywith an outer peripheral part of the sintered part; and a parting lineis provided on a ridge line intersecting an end surface of the exteriorpart which is positioned at one end part side of at least either one ofthe first end part and the second end part and an outer peripheralsurface of the exterior part.

According to the present invention, since the movable die moves alongthe parting surface of the forming die, it is possible to push thesintered part against the fixed die by the movable die so that the fixeddie and the movable die are reliably abutted to the sintered part evenif the height of the sintered part is irregular. Accordingly, theparting surface is prevented from being covered with the material of theexterior part and the burrs are prevented.

Moreover, since the parting line is formed on the ridge line but not onthe outer peripheral surface and the end surfaces of the exterior part,the appearance of the insert sintered part can be improved. Furthermore,in a case in which a groove or the protrusion bar is formed on the outerperipheral part of the sintered part, the sintered part and the exteriorpart are integrated in a state of stopping the rotation by the groove orthe protrusion bar of the sintered part.

As one aspect of the method of manufacturing an insert sintered partaccording to the present invention, it is preferable that in the formingstep of the sintered part, an outer-inclined surface on an outerperipheral surface of at least either one of an end part between thefirst end part and the second end part be formed to be reduced in adiameter toward an end surface of the end part, and a concave parthaving a first tapered surface which abuts to the outer-inclined surfacebe formed on at least one of the fixed die and the movable die, and thefirst tapered surface be made to abut the outer-tapered surface in thedie-clamping step.

In this case, the sintered part is preferably a sintered bearing havingone penetrated hole which penetrates the first end part and the secondend part.

As another aspect of the method of manufacturing an insert sintered partaccording to the present invention, it is preferable that in the formingstep of the sintered part, an outer-inclined surface on an outerperipheral surface of at least either one of an end part between thefirst end part and the second end part be formed to be reduced in adiameter toward an end surface of the end part, and a concave parthaving a first tapered surface which abuts to the outer-inclined surfacebe formed on at least one of the fixed die and the movable die, and thefirst tapered surface be made to abut the outer-tapered surface in thedie-clamping step. In this case, the sintered part is preferably asintered bearing.

In the above aspects, since the outer inclined surface provided on theouter peripheral surface of the sintered part is covered by the firsttapered surface or the inner inclined surface provided on the penetratedhole of the sintered part is covered by the second tapered surface, itcan be reliably prevented that at least either one end part of the firstend part and the second end part is covered with the material of theexterior part in a filmy state. Moreover, when the sintered part is asintered bearing, it is possible to prevent the penetrated hole (abearing hole) from being filmy covered with the material of the exteriorpart.

As one aspect of the insert sintered part according to the presentinvention, it is preferable that the end part at least either one of thefirst end part and the second end part of the sintered part protrudefrom the exterior part, and an outer-inclined surface be formed on anouter peripheral surface of the one end part of the sintered part to bereduced in a diameter and an outer-inclined surface toward the endsurface of the one end part. In this case, the sintered part ispreferably a sintered bearing having one penetrated hole whichpenetrates the first end part and the second end part.

As another aspect of the insert sintered part, it is preferable that thesintered part have one penetrated hole which penetrates the first endpart and the second end part, and an inner inclined surface be providedin the penetrated hole to be increased in a diameter toward at leasteither one end surface of an end part between the first end part and thesecond end part. In this case, the sintered part is preferably be asintered bearing.

As one aspect of the insert sintered part, it is preferable that agroove or a protrusion bar be formed on an outer peripheral part of thesintered part.

As another aspect of the insert sintered part, it is preferable that alarge-diameter part having a larger diameter than that of the one endpart be formed on the outer peripheral part of the sintered part and atleast either of a groove or a protrusion bar along an axial direction onan outer peripheral surface of the large-diameter part and the groove orthe protrusion bar along a radial direction on an end surface of thelarge-diameter part be formed.

Advantageous Effects of Invention

The present invention can appropriately integrate a sintered part and anexterior part such as a resin part by insert-molding even in a case inwhich a height of a sintered part such as a sintered bearing isirregular.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view showing an insert bearing of afirst embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a sintered bearing used inthe insert bearing in FIG. 1 .

FIG. 3 is an end-surface view of the sintered bearing in FIG. 2 , seenin an axial direction from a first end part side.

FIG. 4 is a flowchart showing a manufacturing process of the insertbearing of the first embodiment.

FIG. 5 is a vertical cross-sectional view showing a state of forming aformed body in a forming step.

FIG. 6 is a vertical cross-sectional view showing a correction stepwhere a left half is a state of correcting a sintered body and a righthalf is a state in which the sintered body is taken off from acorrection die.

FIG. 7 is a vertical cross-sectional view showing a state of adie-clamping step in an insert-molding step.

FIG. 8 is a vertical cross-sectional view of a sintered bearingaccording to a second embodiment of the present invention.

FIG. 9 is an end-surface view of the sintered bearing in FIG. 9 , seenin an axial direction from a first end part side.

FIG. 10 is a vertical cross-sectional view showing a state of adie-clamping step of the sintered bearing of FIG. 8 .

FIG. 11 is a vertical cross-sectional view of a sintered bearing usedfor an insert bearing according to a third embodiment of the presentinvention.

FIG. 12 is an end-surface view of the sintered bearing of FIG. 11 , seenin an axial direction from a first end part side.

FIG. 13 is a vertical cross-sectional view showing a state of adie-clamping step of a sintered bearing used for an insert bearingaccording to a fourth embodiment of the present invention.

FIG. 14 is a vertical cross-sectional view showing a state of adie-clamping step of a sintered part used for an insert sintered partaccording to a modification of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be explained below. In thefollowing embodiments, a resin part (exterior part) is integrated by aninjection molding (insert molding) with a sintered bearing (sinteredpart).

[First Embodiment] First, an insert bearing (insert sintered part) 1 ofa first embodiment will be explained. In this embodiment, an example inwhich a large-diameter part 13 with a larger outer diameter than one endpart of a sintered bearing 10 is formed in a part on an outer peripheralpart except for one end part of the sintered bearing 10 (sintered part)used for the insert bearing 1 except one end part is explained.

The insert bearing 1 has the cylindrical sintered bearing 10 made of asintered body of metal powder and a resin part 20 (corresponsive to anexterior part of the present invention) formed integrally with the outerperipheral part of the sintered bearing 10, as shown in FIG. 1 .

The sintered bearing 10 has a bearing hole (penetrated hole) 11 whichpenetrates a center, a first end part 12 which is positioned at an upperend part side of the bearing hole 11, and a second end part 15 which ispositioned at a lower end part side of the bearing hole 11, as shown inFIG. 2 and FIG. 3 . That is, the bearing hole 11 is one penetrated holewhich penetrates the first end part 12 and the second end part 15.

The sintered bearing 10 has the large-diameter part 13 which is largerthan the first end part 12 in the outer diameter and extends from amiddle part to the second end part 15 in an axial direction. An endsurface (a second end surface 10 b) of the sintered bearing 10 at thesecond end part 15 side is formed in a flat-surface shape without steps.

The first end part 12 is formed on the sintered bearing 10 in a taperedshape gradually expanded in diameter from the end surface (the first endsurface 10 a) at the first end part 12 side toward the large-diameterpart 13. The tapered surface (outer-inclined surface 12 a) is formed tohave a slope of 15° (taper angle 30°) for example, and a part thereof isprotruded from the resin part 20.

Both end parts of the bearing hole 11 are chamfered, and taperedsurfaces 11 a and 11 b are formed so that the outer diameter isgradually enlarged respectively toward the first end surface 10 a andthe second end surface 10 b. The tapered surfaces 11 a and 11 bcorrespond to an inner-inclined surface of the present invention, andare formed in an afore-mentioned forming step or a correction step, orby mechanical machining (cutting) or the like after the correction step.

On an outer peripheral surface of the large-diameter part 13, aplurality (four) of grooves 14 along the axial direction are formed overwhole length of the large-diameter part 13, i.e., from the first endsurface 10 a to the second end surface 10 b. Both ends of thelarge-diameter part 13 are chamfered respectively. The four grooves 14are formed at intervals of 90°, as shown in FIG. 3 . These grooves 14are formed to have a shape in which a deepest part is formed in aconcave circular-arc surface, and both sides of it are connected by aconvex circular-arc surface to the outer peripheral surface of thelarge-diameter part 13.

Although an example of only the grooves 14 are formed is shown in thepresent embodiment, protrusion bars projecting in a radial direction maybe formed on the large-diameter part 13 along the axial direction forexample.

In the sintered bearing 10, as shown in FIG. 1 , the outer peripheralpart except a tip end part (the vicinity of the first end surface 10 a)of the first end part 12 is implanted in the resin part 20. That is, theresin part 20 is provided on the outer peripheral part of the sinteredbearing 10 to expose the tip end of the first end part 12 and cover thebase end (root part) of the first end part 12 and the large-diameterpart 13.

That is, a bearing-holding part 21 of the resin part 20 is fixedintegrally on the outer peripheral part of the sintered bearing 10. Thebearing-holding part 21 is formed to have substantially a same height asa whole height of the sintered bearing 10, and the sintered bearing 10is implanted there from the middle position of the first end part 12over a whole of the large-diameter part 13. Accordingly, both endsurfaces of the large-diameter part 13 are covered with thebearing-holding part 21. The resin part 20 also has a bracket 22 whichis formed integrally with the bearing-holding part 20 and connected tothe other parts.

A method of manufacturing the insert bearing 1 formed as above (a methodof manufacturing an insert sintered part) will be explained.

When the insert bearing 1 is manufactured, as shown in a flowchart ofFIG. 4 , a forming step of a sintered part forming the sintered bearing10 by powder molding, and an insert-molding step disposing the sinteredbearing formed by the forming step of the sintered part in aninjection-molding die 60 (corresponding to a forming die of the presentinvention) to form the resin part 20 integrally with the outerperipheral part of the sintered bearing 10 by injection-molding arecarried out. It will be described in order of steps below.

<Forming Step of Sintered Part>

The forming step of sintered part has a forming step to form a formedbody 10P to be the sintered bearing 10, a sintering step to form asintered body (not illustrated) by sintering the formed body 10P, and acorrection step (sizing step) to size the sintered body.

(Forming Step)

A forming die to form the formed body 10P is provided with a die 42 inwhich a circular penetrated hole 41 is formed, a core rod 43 disposed inthe penetrated hole 41, an outer first upper punch 44 and an innersecond upper punch 46 which are disposed between the penetrated hole 41and the core rod 43, and a first lower punch 45 facing to the firstupper punch 44 and the second upper punch 46, as shown in FIG. 5 . Thesepunches 44 to 46 are formed in concentric cylindrical shape around thecore rod 43 as a center.

A space made by the die 42, the core rod 43, and the first lower punch45 is filled with powder, and compressed by the upper and lower punches44 to 46, so that the formed body 10P is made. At this time, a tip endof the first upper punch 44 has a shape having an inclined surface asshown in FIG. 5 , and a distance between the first lower punch 45 andthe second upper punch 46 is larger than a distance between the firstlower punch 45 and the first upper punch 44, so that the formed body 10Phaving a large-diameter part 13P on an outer peripheral part is formed.A penetrated hole 11P is formed into a penetrated state by the core rod43.

(Sintering Step)

A sintered body is formed by heating the formed body 10P to sinter thepowder.

(Correction Step)

The sintered body is corrected (sizing) by a correction die 80. In thiscorrection step, the grooves 14 are formed on the outer peripheral partof the large-diameter part 13 with finishing the external form into afinal dimension.

As shown in FIG. 6 , the correction die 80 is provided with a die 82 inwhich a circular penetrated hole 81 is formed, a core rod 83 which isdisposed in the penetrated hole 81, an outer first upper punch 84 and afirst lower punch 85 and an inner second upper punch 86 and a secondlower punch 87 which are disposed between the penetrated hole 81 and thecore rod 83 so that they make pairs of the upper one and the lower onerespectively.

On an inner peripheral surface of the penetrated hole 81 of the die 82,a plurality of protrusion bars 88 penetrating along the axial directionare formed with being spaced each other in a circumference direction.Corresponding to these protrusion bars 88, grooves 89 in which theprotrusion bars 88 are slidably fitted are formed with being spaced eachother in the circumference direction on an outer peripheral part of thefirst upper punch 84 and the first lower punch 85.

The sintered body is corrected by pushing the sintered body into thespace between the die 82 and the core rod 83 with pressurizing in theaxial direction by the first punches 84 and 85 and the second punches 86and 87. By arranging the sintered body in the correction die 80 tocorrect, the grooves 14 along the axial direction are formed on theouter peripheral part of the large-diameter part 13 to correspond to theprotrusion bars 88 of the die 82 with being spaced in thecircumferential direction.

The tapered surfaces 11 a and 11 b of the bearing hole 11 are formed bymachining (cutting) and the like after the correction step.

In addition, although the grooves 14 are formed after the correctionstep in the forming step of the sintered part in the present embodiment,it is not limited to this, the grooves 14 may be formed in the formingstep. Moreover, the tapered surfaces 11 a and 11 b of the bearing hole11 may also be formed in the forming step or the correction step.

Furthermore, the outer-inclined surface 12 a may also be formed in anyof the forming step, the correction step, or the machining after thecorrection step.

<Insert-Molding Step>

The sintered bearing 10 formed as above is integrated with the resinpart 20 in the insert-molding step. The insert-molding step has adie-clamping step (corresponding to the die-clamping step of the presentinvention) in which the sintered bearing 10 is disposed in theinjection-molding die 60 in a state in which a cavity 61 is formedoutside the sintered bearing 10, and an injection step injecting meltedresin (corresponding to the melted material of the present invention) tobe the resin part 20 into the cavity 61.

(Die-Clamping Step)

The injection-molding die 60 has a fixed die 62 and a movable die 63 asshown in FIG. 7 ; the sintered bearing 10 is held between the fixed die62 and the movable die 63 and the cavity 61 is formed, by closing(clamping) the fixed die 62 and the movable die 63. A parting surface620 between the fixed die 62 and the movable die 63 is formed along adirection of movement of the movable die 63 (a vertical direction inFIG. 7 ). The sintered bearing 10 is held between the fixed die 62 andthe movable die 63, and the cavity 61 which is filled with the meltedresin is formed on the outer peripheral part of that sintered bearing10.

In the fixed die 62, a concave part 64 having a first tapered surface641 which abuts on the outer-inclined surface 12 a of the sinteredbearing 10 is formed.

The movable die 63 moves along the parting surface 620 so that thesintered bearing 10 is pushed against the fixed die by the movable die63. Accordingly, even if the height of the sintered bearing 10 isirregular, the first end part 12 is held in the concave part 64 of thefixed die 62 in a fit-insert state up to a middle position in a lengthdirection. Thereby the inner peripheral surface of the concave part 64including the first tapered surface 641 abuts on the outer-inclinedsurface 12 a of the sintered bearing 10 at a whole circumference.

On the second end surface 10 b (an end surface at the second end part15), an end surface of a protrusion part 65 protruding from the innersurface of the movable die 63 abuts. The cavity 61 is provided with abearing-holding space 66 formed surrounding the outer circumference ofthe sintered bearing 10 and a connection part 67 connected to thebearing-holding space 66. The sintered bearing 10 is held in thebearing-holding space 66 with exposing the outer peripheral surface andthe end surface of the large-diameter part 13, and the base end part(the vicinity of the large-diameter part 13) of the first end part 12.To the cavity 61, a plunger (not illustrated) to which a sprue 68 inwhich the melted resin is supplied is connected via a gate 69 isconnected to inject the melted resin to the sprue 68.

(Injection Step)

The melted resin is injected into the cavity 61 of the injection-moldingdie 60 which is clamped. At this time, a tip end of the first end part12 of the sintered bearing 10 is fit-inserted in the concave part 64 ofthe fixed die 62; and the second end surface 10 b abuts on theprotrusion part 65. Although the injection pressure is applied in thecavity 61, the tip end of the first end part 12 is not exposed in thecavity 61; accordingly, the injection pressure is applied on the outersurface except the tip end of the first end part 12 of the sinteredbearing 10. Accordingly, the melted resin does not leak out to the firstend surface 10 a of the sintered bearing 10.

If the injection pressure rises and the melted resin leaks out from theparting surface 620, a parting line (not illustrated) is formed on theouter peripheral surface of the exterior part 20; however, since theparting surface 620 of the die 60 is formed along the movement directionof the movable die 63 as shown in FIG. 7 , the parting line of the resinpart 20 is formed on the crossing ridge line between the outerperipheral surface and the end surface, so that it does hardly notconcern the appearance of the resin part 20.

Since the movable die 63 moves along the parting surface 620, even ifthe height of the sintered bearing 10 is irregular, the fixed die 62 andthe movable die 63 can abut on the sintered bearing 10. Thereby it isprevented that the abutted part of the fixed die 62 and the movable die63 is filmy covered with the melted material and burrs are generated onthe parting line.

In the insert bearing 1 formed as above, as shown in FIG. 1 , the centerpart of the sintered bearing 10 except the tip end of the first end part12 and including the large-diameter part 13 is surrounded by the resinpart 20: the rotation between the sintered bearing 10 and the resin part20 is stopped by the grooves 14, and the resin part 20 covers both endsof the large-diameter part 13 so that they are integrated not to bedropped off in the axial direction. Moreover, it is different from thesintered bearing described in the prior art: since resin films are notformed on both end surface and the parting line is formed on the ridgeline, the appearance is not deteriorated and it is also restrained tointerfere with the other parts.

Second Embodiment

FIG. 8 and FIG. 9 are views showing a sintered bearing 110 used for aninsert bearing of a second embodiment. FIG. 10 is a view showing a stateof a die-clamping step in a manufacturing process of the insert bearingof the second embodiment. The sintered bearing 110 of this presentembodiment is formed to a cylindrical shape which does not have thelarge-diameter 13 provided at the sintered bearing 10 of the firstembodiment. In addition, in embodiments after this second embodiment,common elements to the first embodiment are denoted by the same symbolsand the description is simplified.

As shown in FIG. 8 and FIG. 9 , the sintered bearing 110 has a bearinghole (penetrated hole) 111 which penetrates the center, a first end part112 positioned at the upper end part side of the bearing hole 111, and asecond end part 115 positioned at the lower end part side of the bearinghole 111. Both end parts of the bearing hole 111 are chamfered; andtapered surfaces 111 a and 111 b are formed so that the outer diameteris gradually enlarged respectively toward an end surface 110 a of thefirst end part 112 and an end surface 110 b of the second end part 115.The tapered surfaces 111 a and 111 b correspond to the inner-inclinedsurface of the present invention, and are formed in the forming step orthe correction step, or by mechanical machining (cutting) or the likeafter the correction step.

On an outer peripheral surface of the sintered bearing 110, a plurality(four) of grooves 114 along the axial direction. Specifically, fourgrooves 114 which are shorter than a half of a height of the sinteredbearing 110 are formed on the outer peripheral surface at the first endpart 112 side. These grooves 114 are formed to have a shape in which adeepest part is formed in a concave circular-arc surface, and both sidesof it are connected to the outer peripheral surface of the sinteredbearing 110. These four grooves 114 are formed at intervals of 90°, asshown in FIG. 9 .

A method of manufacturing the insert bearing according to the secondembodiment is substantially the same as the method of manufacturing theinsert bearing 1 of the above-described first embodiment; however, apart of the shape of an injection-molding die used for the die-clampingstep and the insert-molding step is different. It will be explained indetail below.

An injection-molding die 60A has a fixed die 62A and a movable die 63Aas shown in FIG. 10 ; the sintered bearing 110 is held between the fixeddie 62A and the movable die 63A by closing (clamping) the fixed die 62Aand the movable die 63A, and the cavity 61 where the melted resin isfilled is formed on the outer peripheral part of the sintered bearing110.

In the sintered bearing 110, a second protrusion part 65A of the movabledie 63A is fit-inserted in the bearing hole 111 at the second end part115 side, so that a second tapered surface 651 of the second protrusionpart 65 abuts to the tapered surface 111 b of the bearing hole 111 at awhole circumference. An end surface of a first protrusion part 64Aprotruding from an inner surface of the fixed die 62A abuts to the firstend surface 110 a.

The cavity 61 is provided with a bearing-holding space 66 formedsurrounding the outer circumference of the sintered bearing 110 and aconnection part 67 connected to the bearing-holding space 66. Thesintered bearing 110 is held in the bearing-holding space 66 withexposing the outer peripheral surface, a part of the first end surface110 a, and the second end surface 111 b. To the cavity 61, a plunger(not illustrated) to which a sprue 68 in which the melted resin issupplied is connected via a gate 69 is connected to inject the meltedresin to the sprue 68.

The melted resin is injected into the cavity 61 of the injection-moldingdie 60A which is clamped. At this time, the second protrusion part 65Aof the movable die 63A is fit-inserted in the bearing hole 111 at thesecond end part 115 side of the sintered bearing 110; so that the tipend of the second protrusion part 65A is fit-inserted, and the first endpart 112 abuts on the first protrusion part 64A. Although the injectionpressure is applied in the cavity 61, the tapered surface 111 b of thebearing hole 111 at the second end part 115 side abuts on the secondtapered surface 651 of the second protrusion part 65A and this part isnot exposed in the cavity 61, so that the injection pressure is appliedon the outer surface except the tapered surface 111 b of the bearinghole of the sintered bearing 110.

Accordingly, the melted resin does not leak to a part at the second endpart 115 side in the bearing hole 111 of the sintered bearing 110. Ifthe injection pressure rises and the melted resin leaks out from theparting surface 620, a parting line (not illustrated) is formed on theouter peripheral surface of the exterior part; however, since theparting surface 620 of the die 60A is formed along the movementdirection of the movable die 63A as shown in FIG. 10 , the parting lineof the resin part is formed on the crossing ridge line between the outerperipheral surface and the end surface, so that it does hardly notconcern the appearance of the resin part.

Third Embodiment

FIG. 11 and FIG. 12 show a sintered bearing 210 used for an insertbearing of a third embodiment.

The sintered bearing 210 of this embodiment is provided with a bearinghole (penetrated hole) 211 which penetrates the center, a first end part212 positioned at an upper end part side of the bearing hole 211, and asecond end part 215 positioned at a lower end part side of the bearinghole 211, as shown in FIG. 11 and FIG. 12 , as in the second embodiment.On both end parts of the bearing hole 211, tapered surfaces(inner-inclined surfaces) 211 a and 211 b are formed in the forming stepor the correction step, or by the mechanical machining (cutting) or thelike after the correction step.

Grooves 214 formed in the sintered bearing 210 are formed four on an endsurface of the first end part 212 at intervals of 90° in a shapeextending in a radius direction, as shown in FIG. 11 and FIG. 12 . Thesegrooves 214 are formed to have a shape in which a deepest part is flat,and has inclined surfaces which are gradually expanded from the deepestpart toward the upper side.

The sintered bearing 210 of this embodiment is different from the secondembodiment only in the shape of the grooves 214, so the insert bearingis formed by using the same injection-molding die 60A as in the secondembodiment. Accordingly, also in the present embodiment, the same effectas in the second embodiment can be obtained.

Fourth Embodiment

FIG. 13 is a view showing a state of die-clamping step in a method ofmanufacturing an insert bearing of a fourth embodiment.

A sintered bearing 310 of the fourth embodiment differs from the firstto third embodiments, and is a pivot bearing formed in a solid state: asshown in FIG. 13 , a first end part 312, a second end part 315, and alarge-diameter part 313 which is larger than the first end part 312 inan outer diameter are provided.

The first end part 312 is formed in a tapered shape in which the outerdiameter is gradually reduced from the large-diameter part 313 towardthe end surface. The tapered surface (the outer-inclined surface 312 a)is formed to have a slope of 15° (taper angle 30°) for example.

The sintered bearing 310 is put in an injection-molding die 60C andformed into an insert bearing. The movable die 63 moves along theparting surface 620, so that the sintered bearing 310 is pressed againsta fixed die 62C by the movable die 63. Accordingly, even if the heightof the sintered bearing 310 is irregular, the first end part 312 is heldin a concave part 64C of the fixed die 62C in a fit-insert state up to amiddle position in a length direction.

Thereby the inner peripheral surface of the concave part 64C includingthe first tapered surface 641C abuts on the outer-inclined surface 312 aof the sintered bearing 310 at a whole circumference. On an end surfaceof the second end part 315, the end surface of the protrusion part 65protruding from the inner surface of the movable die 63 abuts.

The melted resin is injected into the cavity 61 of the injection-moldingdie 60C which is die-clamped. At this time, a tip end of the first endpart 312 of the sintered bearing 310 is fit-inserted in the concave part64C of the fixed die 62C; and the second end part 315 abuts on theprotrusion part 65. Although the injection pressure is applied in thecavity 61, the tip end part of the first end part 312 is not exposed inthe cavity 61; accordingly, the injection pressure is applied on theouter surface except the tip end part of the first end part 312 of thesintered bearing 310.

The parting surface 620 of the die 60C is formed along the movementdirection of the movable die 63 as shown in FIG. 13 , the parting lineof the resin part is formed on the crossing ridge line between the outerperipheral surface and the end surface, so that it does hardly notconcern the appearance of the resin part.

Accordingly, even if the sintered bearing 310 does not have a bearinghole, similar effects as in the above-described embodiments can beobtained.

In addition, the present invention is not limited to the structures ofthe above-described embodiments and various modifications may be made indetailed structures without departing from the scope of the presentinvention.

For example, in the first embodiment, the outer-inclined surface 12 a ofthe first end part 12 is put in the concave part 64 of the fixed die 62,and the second end part 15 abuts on the protrusion part 65 of themovable die 63 (the tapered surface of the die abuts on one taperedsurface of the bearing hole and does not abut on the other taperedpart); it is not limited to this, as in the second embodiment, thestructure in which the tapered surface 111 b of the bearing hole 111abuts on the second tapered surface 651 (a structure in which thetapered surface of the die abuts on both tapered surfaces of the bearinghole) may be applied. In this case, it is reliably restrained that theresin material enters in the bearing hole from both sides.

Examples in which the grooves are formed on the end surface, the outerperipheral surface, or the large-diameter part of the sintered bearingare shown in the first to fourth embodiments; protrusion bars instead ofthe grooves may be formed. Several grooves and protrusion bars arepreferably formed with a space in a circumference direction; however,only one may be formed.

Moreover, embodiments in which the exterior parts are formed byinjection-molding resin were explained; however, the present inventionmay be applied for a case in which an exterior part is formed by castingmetal such as aluminum alloy and the like. In this case, the sinteredpart is disposed in a casting die (a forming die) and di-clamped(die-clamping step) and a cavity around it is filled with melted metal(melted material) which becomes the exterior part (injection step), sothat the sintered bearing and the metal exterior part are integrated.

In the first to fourth embodiments, the sintered bearings wereexemplified as the sintered parts and the insert bearings wereexemplified as the insert sintered part; however, the sintered part isnot limited to a bearing but may be a bulb sheet, a bush, and the like.That is, the present invention can be applied for sintered parts notonly for sintered bearings: it can be applied for all products in whichthe sintered part is integrated with the exterior part.

For example, the sintered part may be a sintered part 410 having arectangular-plate shape as shown in FIG. 14 . In this case, in aninjection-molding die 60D, it is enough that a first end part 412 of thesintered part 410 abuts on a first protrusion part 64D of a fixed die62D, and a second end part 415 abuts on a second protrusion part 65D ofthe movable die 63. That is, even if the outer-inclined surface and theinner-inclined surface are not formed in the sintered part, it is ascope of rights of the present invention.

INDUSTRIAL APPLICABILITY

Even if a height of a sintered part such as a sintered bearing isirregular, a sintered part and an exterior part such as a resin part canbe appropriately integrated by insert-molding.

REFERENCE SIGNS LIST

-   1 Insert bearing (Insert sintered part)-   10, 110, 210, 310 Sintered bearing (Sintered part)-   410 Sintered part-   10P Formed body-   11, 111, 211 Bearing hole (Penetrated hole)-   11 a, 11 b, 111 a, 111 b, 211 a, 211 b Tapered surface    (Inner-inclined surface)-   12, 112, 212, 312 First end part-   15, 115, 215, 315, 415 Second end part-   12 a, 312 a Outer-inclined surface-   13, 313 Large-diameter part-   14, 114, 214 Groove-   20 Resin part (Exterior part)-   21 Bearing-holding part-   40 Forming die-   80 Correction die-   60, 60A, 60C, 60D Injection-molding die (Forming die)-   61 Cavity-   62, 62A, 62C Fixed die-   63, 63A Movable die-   64, 64C Concave part-   641, 641C First tapered surface-   64A, 64D First protrusion part-   65 Protrusion part-   65A, 65D Second protrusion part-   651 Second tapered surface-   66 Bearing-holding space-   67 Connection part-   68 Sprue-   69 Gate

1. A method of manufacturing an insert sintered part comprising: aforming step of a sintered part forming a sintered part having a firstend part and a second end part by powder molding; and an insert-moldingstep of forming an insert sintered part in which an exterior part isintegrated to an outer peripheral part of the sintered part, wherein aforming die used in the step of insert-forming includes a fixed die anda movable die; a parting surface in which the fixed die and the movabledie abut is formed along a movement direction of the movable die, andthe step of insert-forming has: a die-clamping step in which thesintered part is held between the fixed die and the movable die, themovable die is moved along the parting surface, and the sintered part ispressed against the fixed die by the movable die, to form a cavityaround the sintered part by covering a region of the sintered part witha gap excepting a part where the first end part abutting the fixed part,and a part where the second part abutting the movable die; and a fillingstep after the die-clamping step filling the cavity with a meltedmaterial being formed into the exterior part.
 2. The method ofmanufacturing an insert sintered part according to claim 1, wherein inthe forming step of the sintered part, an outer-inclined surface on anouter peripheral surface of at least either one of an end part betweenthe first end part and the second end part is formed to be reduced in adiameter toward an end surface of the end part, and a concave parthaving a first tapered surface which abuts to the outer-inclined surfaceis formed on at least one of the fixed die and the movable die, and thefirst tapered surface is made to abut the outer-tapered surface in thedie-clamping step.
 3. The method of manufacturing an insert sinteredpart according to claim 1, wherein in the forming step of the sinteredpart, one penetrated hole which penetrates the first end part and thesecond end part is formed and an inner-inclined surface is formed in thepenetrated hole to be increased in a diameter toward at least either oneend surface of one end part between the first end part and the secondend part, a protruded part having a second tapered surface which abutsto the inner-inclined surface is formed on at least one of the fixed dieand the movable die, and in the die-clamping step, the second taperedsurface is made abut to the inner inclined surface.
 4. The method ofmanufacturing the insert sintered part according to claim 3, wherein thesintered part is a sintered bearing.
 5. The method of manufacturing theinsert sintered part according to claim 1, wherein the sintered part isa sintered bearing having one penetrated hole which penetrates the firstend part and the second end part.
 6. An insert sintered part comprising:a sintered part having a first end part and a second end part; and anexterior part which is formed integrally with an outer peripheral partof the sintered part, wherein a parting line is provided on a ridge lineintersecting an end surface of the exterior part which is positioned atone end part side of at least either one of the first end part and thesecond end part and an outer peripheral surface of the exterior part. 7.The insert sintered part according to claim 6, wherein the end part atleast either one of the first end part and the second end part of thesintered part protrudes from the exterior part, and an outer-inclinedsurface is formed on an outer peripheral surface of the one end part ofthe sintered part to be reduced in a diameter and an outer-inclinedsurface toward the end surface of the one end part.
 8. The insertsintered part according to claim 6, wherein the sintered part has onepenetrated hole which penetrates the first end part and the second part,and an inner inclined surface is provided in the penetrated hole to beincreased in a diameter toward at least either one end surface of an endpart between the first end part and the second end part.
 9. The insertsintered part according to claim 8, wherein the sintered part is asintered bearing.
 10. The insert sintered part according to claim 6,wherein the sintered part is a sintered bearing having one penetratedhole which penetrates the first end part and the second end part. 11.The insert sintered part according to claim 6, wherein a groove or aprotrusion bar is formed on an outer peripheral part of the sinteredpart.
 12. The insert sintered part according to claim 7, wherein alarge-diameter part having a larger diameter than that of the one endpart is formed on the outer peripheral part of the sintered part, and atleast either of a groove or a protrusion bar along an axial direction onan outer peripheral surface of the large-diameter part and the groove orthe protrusion bar along a radial direction on an end surface of thelarge-diameter part is formed.
 13. The method of manufacturing theinsert sintered part according to claim 2, wherein the sintered part isa sintered bearing having one penetrated hole which penetrates the firstend part and the second end part.
 14. The insert sintered part accordingto claim 7, wherein the sintered part is a sintered bearing having onepenetrated hole which penetrates the first end part and the second endpart.
 15. The insert sintered part according to claim 8, wherein agroove or a protrusion bar is formed on an outer peripheral part of thesintered part.
 16. The insert sintered part according to claim 9,wherein a groove or a protrusion bar is formed on an outer peripheralpart of the sintered part.